Well drilling bits and particularly oil well drilling bits are very well known devices of which there is a very important variety with different designs and special characteristics for use in all the possible conditions of operation of the same for drilling down to find oil, water and the like.
However, up to the present time it has been customary that, when the bit is worn out by use of the same, the whole drilling string has to be disassembled and extracted from the length of well already drilled in order to replace the bit and resume the drilling operation, after placing the bit on the tip of the drilling string and reassembling the same to continue drilling.
This has been a considerable drawback of all the drilling bits known in the prior art, inasmuch as the trend of the workers in the art has been towards the obtention of more resistant drilling bits in order to lengthen the operational life thereof to thus avoid frequent removals of the drilling string and the worn out bit, which is obviously a costly and cumbersome operation.
It has been thought in the past that providing a mechanism for retracting a bit might cause considerable problem in the normal drilling operation, whereby the research activities in this field have gone, as mentioned above, in a different direction and have rather been towards the obtention of better materials than towards the design of a mechanism for retracting a drilling bit with the purpose of preventing the up to now necessary string disassembling operation which has caused so many problems in the drilling art.
To the knowledge of applicant, there is no retractable drilling bit in the prior art that may have been designed appropriately to serve its function in an efficient manner, whereby the drilling art is in high need of said type of a drilling bit, in order to avoid unnecessary cost increases caused by the necessity of disassembling the string for replacing the bit, particularly when the well has been drilled down to a considerable depth.